Capacitors are one of the most versatile passive components in electronics. They are used for energy storage, filtering, timing, tuning, and noise suppression. The many types of capacitors differ by their dielectric material, structure, tolerance, and application area.
This article organizes them into Fixed, Variable, and Specialty groups, covering both common and advanced families.
Fixed Capacitors
Ceramic Capacitors
These components use a ceramic material as the dielectric. Class 1 types, such as C0G (NP0), are valued for their high stability and low losses, making them suitable for precision applications in RF circuits, oscillators, and timing circuits. Class 2 and 3 ceramics, like X5R and X7R, offer higher capacitance in a smaller footprint due to their higher dielectric constant, though they are less stable with temperature fluctuations. Their primary use is in decoupling circuits, where they filter high-frequency noise from power lines, and as general-purpose bypass capacitors on circuit boards, particularly in the form of multilayer ceramic chips (MLCCs).
Film Capacitors
Comprised of thin plastic films (polyester, polypropylene, or PTFE), film capacitors are known for their stable electrical properties, low Equivalent Series Resistance (ESR), and long operational life. Polypropylene capacitors are favored in audio and AC motor circuits for their low loss characteristics, while polyester types serve as a general-purpose, cost-effective alternative. In power electronics, these capacitors function as snubbers, protecting semiconductor switches from damaging voltage spikes.
Thin Film Capacitors
This type of capacitor is manufactured using highly precise vacuum deposition techniques to create ultra-thin dielectric layers. The result is a component with exceptional precision and excellent performance at very high frequencies. Their applications are concentrated in high-frequency circuit design, such as impedance matching and filtering, and in sensitive instrumentation where precision and stability are paramount.
Mica and PTFE Capacitors
Utilizing mica or PTFE as the dielectric, these capacitors exhibit remarkable stability and low losses. Mica capacitors are particularly noted for their high quality factor (Q) and are indispensable in stable RF oscillators and precision filters. PTFE capacitors, with their superior thermal and electrical properties, are used in very demanding applications, including aerospace systems.
Glass Capacitors
Constructed with a glass dielectric, these components are hermetically sealed and highly resistant to environmental degradation. Their exceptional stability, high insulation resistance, and very high voltage ratings make them suitable for mission-critical applications where failure is unacceptable. They are commonly found in aerospace, military, and nuclear systems where radiation hardening and extreme reliability are required.
Paper Capacitors (Obsolete)
Historically, these capacitors were created by rolling up strips of metal foil and paper, which was then impregnated with a material like wax or oil to enhance insulation. While largely replaced by modern capacitor types, they are still used by enthusiasts in the restoration of vintage radios and tube amplifiers to maintain historical accuracy and a specific audio aesthetic.
Aluminum Electrolytic Capacitors
These are polarized capacitors that provide very high capacitance at a low cost. They consist of an aluminum foil anode and a liquid electrolyte. Their primary function is in power supply units, where they smooth rectified DC voltage, and in audio circuits for coupling and power filtering.
Wet Aluminum Capacitors
A subtype of aluminum electrolytic capacitors, these are distinguished by their liquid-soaked electrolyte. They are typically large and used in high-voltage industrial applications and older designs where massive capacitance is needed for power supply filtering or motor starting.
Aluminum – Polymer Capacitors
Unlike their wet counterparts, these capacitors use a solid, conductive polymer as the electrolyte. This results in a significantly lower ESR and a high ripple current rating, making them ideal for high-speed switching power supplies and for filtering power rails for processors and other high-current components on motherboards.
Tantalum Capacitors
Polarized and featuring a dielectric of tantalum oxide, these capacitors offer a very high capacitance-to-volume ratio, making them compact and suitable for space-constrained designs. Their small size and reliability are a benefit in portable electronics, medical devices, and aerospace systems.
Tantalum – Polymer Capacitors
By combining tantalum’s high capacitance density with a conductive polymer electrolyte, these components achieve an even lower ESR than traditional tantalum capacitors. This makes them highly effective in filtering power for high-speed digital and telecom equipment.
Niobium Oxide Capacitors
This is a modern alternative to tantalum capacitors. They are similar in construction but are notable for their safer failure mode, which is typically an open circuit rather than a short. This makes them a more reliable choice for portable and consumer electronics where safety is a key concern.
Supercapacitors (EDLC, Ultracapacitors)
These are not conventional capacitors but rather energy storage devices that can store a very high amount of charge. They operate on an electrochemical principle and can be charged and discharged rapidly. They are used for short-term power backup, in regenerative braking systems, and to provide high current bursts for devices like camera flashes.
Hybrid Supercapacitors
These capacitors combine the high power density of an electric double-layer capacitor with the higher energy density of a pseudocapacitor. They are an ideal solution for applications where both high power output and good energy storage are needed, such as in certain electric vehicle or industrial power systems.
Silicon Capacitors
Fabricated using standard semiconductor processes, silicon capacitors are exceptionally small, stable, and have very low leakage current. Their precise and compact nature makes them suitable for use in medical implants, on-chip RF circuits, and other applications where high reliability and miniaturization are essential.
Capacitor Networks / Arrays
These are single-package components that house multiple capacitors, typically for use on SMD PCBs. They help to save board space and simplify assembly by providing multiple filtering or decoupling capacitors in one compact part. They are widely used in high-density digital circuit designs.
Stacked Capacitors (MLCCs)
A manufacturing technique used to create MLCCs with a very high capacitance. By stacking many layers of dielectric and electrode plates, a high capacitance can be achieved in a small volume. They are the most common capacitor type in modern electronics, from smartphones to IoT devices.
| Type | Description | Typical Applications |
|---|---|---|
| Ceramic Capacitors | Use ceramic dielectric; Class I (stable), Class II/III (high capacitance) | Decoupling, filtering, RF |
| Film Capacitors | Use plastic films (polyester, polypropylene, PTFE); stable, low ESR | Audio, motor drives, power supplies |
| Aluminum Electrolytic | Polarized; high capacitance; liquid electrolyte | Power filtering, bulk energy storage |
| Aluminum-Polymer | Solid polymer electrolyte; lower ESR than liquid types | High-speed digital, VRMs |
| Tantalum Capacitors | Compact, stable; polarized; solid electrolyte | Space-constrained, high-reliability circuits |
| Tantalum-Polymer | Use conductive polymer; better ESR and ripple handling | Mobile devices, SSDs |
| Niobium Oxide | Safer failure mode than tantalum; solid electrolyte | Portable electronics |
| Mica Capacitors | Use natural mica dielectric; extremely stable | RF, timing, precision analog |
| PTFE Capacitors | Use Teflon dielectric; high temperature and stability | Aerospace, RF |
| Silicon Capacitors | Thin-film silicon dielectric; ultra-stable and compact | Medical, automotive, RF |
| Thin Film Capacitors | Use vacuum-deposited layers; high precision | Instrumentation, aerospace |
| Electric Double Layer (EDLC) | Supercapacitors; store energy via double-layer mechanism | Backup power, energy harvesting |
| Capacitor Networks / Arrays | Multiple capacitors in one package; saves PCB space | Decoupling in dense PCBs |
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